Question about TP-Link Re450

So-called WiFi range extenders are outdated technology and often do not offer a stable connection, it is better to buy a real WiFi mesh system that also offers sufficient coverage. This one consists of 2 WiFi routers with a built-in 3 x Gbit switch and offers excellent performance at a very low price:

Xiaomi AX3000

With a WiFi mesh system, the WLAN devices always choose the router with the strongest transmission, and this without interruption. With a range extender, the devices starve at an extender until the connection is interrupted, there is an interruption and then you have to see how it gets connected again, usually it takes a few seconds until a WiFi device has registered at another extender. Extenders also generally reduce the transfer rate, which is why I generally advise against using extenders.